Video processing method and related devices

ABSTRACT

A video processing method and related devices are provided. The method includes: acquiring board writing images of consecutive frames from a video with unobstructed board writing; calculating a difference area between the image of a current frame and a reference image; replacing a corresponding image block in the board writing image of the current frame with a corresponding image block in the reference image to obtain a new board writing image for each of the difference area; outputting the new board writing image to form a new video. The board writing image of the current frame are sequentially each board writing image after the board writing image of a first frame in the board writing images of the consecutive frames, and the reference image is the board writing image associated with a previous board writing image.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to the Chinese Patent Application No.202210396715.8, filed on Apr. 15, 2022, entitled “video processingmethod and related devices”, and published as CN114945107A on Aug. 26,2022, which is incorporated herein by reference in its entirety in thisdisclosure.

BACKGROUND OF THE DISCLOSURE Field of Technology

The present disclosure relates to a field of electronic teaching, and inparticular, to a video processing method and related devices.

Description of the Related Art

With universal and popularization of online classes, videos for teachingbecome an indispensable educational resource. The video for teaching isobtained by shooting a teaching scene by a camera. In the teachingscene, a teacher may teach through writing contents on a writing board,and writing contents of the writing board are important forunderstanding videos.

SUMMARY

In order to solve the above technical problem, the present disclosureprovides a video processing method and related devices.

According to a first aspect of the present disclosure, there is provideda video processing method, comprising:

acquiring board writing images of consecutive frames from a video withunobstructed board writing;

calculating a difference area between the board writing image of acurrent frame and a reference image;

replacing a corresponding image block in the board writing image of thecurrent frame with a corresponding image block in the reference image toobtain a new board writing image for each of the difference area;

outputting the new board writing image to form a new video,

wherein the board writing image of the current frame are sequentiallyeach board writing image after the board writing image of a first framein the board writing images of the consecutive frames, and the referenceimage is the board writing image associated with a previous boardwriting image.

Optionally, for the board writing image of a second frame in the boardwriting image of the consecutive frames served as the board writingimage of the current frame, the reference image is the board writingimage of the first frame, and for the board writing image after thesecond frame served as the board writing image of the current frame, thereference image is a new board writing image associated with a previousboard writing image.

Optionally, for the board writing image of a second frame in the boardwriting image of the consecutive frames served as the board writingimage of the current frame, the reference image is an image obtained byfusing images of a plurality of frames without a board writing contentin the video with unobstructed board writing.

Optionally, the video with unobstructed board writing is obtained byfollowing steps: extracting a board writing content from an originalvideo; completing the board writing content shielded by a teacher; andsynthesizing a completed board writing content with the original video.

Optionally, wherein calculating a difference area between the boardwriting image of a current frame and a reference image comprises:

calculating a difference in pixel level between the board writing imageof the current frame and the reference image, and obtaining thedifference area based on pixels with the difference larger than adifference threshold value, or,

dividing the board writing image of the current frame and the referenceimage into a plurality of image blocks respectively, and taking theimage block with a difference of the image blocks larger than adifference threshold as the difference area.

Optionally, further comprising: expanding an irregular shaped differencearea to a regular shaped difference area.

Optionally, further comprising: adjusting a color of a writing board inthe new board writing image.

Optionally, adjusting a color of a board in the new board writing imagecomprises:

obtaining a corrected board writing image, wherein the corrected boardwriting image only comprises a writable effective area, and comprise noframe of the writing board and no board writing content;

calculating an average value of each color channel of the correctedboard writing image or obtaining a constant value of each color channelpreset by a user;

for a dark color writing board, modifying a pixel value of each colorchannel in the new board writing image, which is smaller than a firstthreshold value, into an average value of the color channel or aconstant value of each color channel preset by a user; and

for a light color writing board, modifying a pixel value of each colorchannel in the new board writing image, which is larger than the secondthreshold value, into an average value of the color channel or aconstant value of each color channel preset by a user.

According to a second aspect of the present disclosure, there isprovided a video processing device, comprising:

a board writing debouncing module for performing the video processingmethod according to any one of claims 1 to 6 and outputting the newboard writing image; and

a board writing background color control module for adjusting a color ofa writing board in the new board writing image.

According to a third aspect of the present disclosure, there is providedan electronic device, comprising: a processor, a memory and a programstored in the memory and executable on the processor, wherein theprogram carries out steps of the video processing method according toany one of claims 1 to 8 when executed by the processor.

According to a forth aspect of the present disclosure, there is provideda computer readable storage medium, a computer program or an instructionis stored in the computer readable storage medium which carries outsteps of the video processing method according to any one of claims 1 to8 when executed by the processor.

The present disclosure provides a video processing method for solving aproblem of writing bounce in the image by associating the board writingimages of consecutive frames. Furthermore, achieving a method forcontrolling a base color of the writing board which is capable ofcontrolling a background color of the writing board in a process oftransparent display of the board writing image, so that the image iscloser to a real scene.

It should be understood that both foregoing general description andfollowing detailed description are exemplary and explanatory only andare not restrictive of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other purposes, features and advantages of the presentdisclosure will be more clear through following descriptions of theembodiments of the present disclosure with reference to accompanyingdrawings, in which:

FIG. 1 is a flowchart of a video processing method according to anembodiment of the present disclosure;

FIG. 2 is for illustrating an exemplary frame image in a video withunobstructed board writing;

FIG. 3 a and FIG. 3 b are for illustrating corresponding image blocks oftwo images in a reference area;

FIG. 4 is a flowchart of a method for converting an image of a boardwriting into a board writing image with a base color of a writing boardaccording to an embodiment of the present disclosure;

FIG. 5 is a schematic diagram of a video processing device according toan embodiment of the present disclosure;

FIG. 6 is a schematic diagram of an electronic device for implementingvarious embodiments of the present disclosure;

FIG. 7 is a schematic diagram of a teaching system according to anembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

To facilitate an understanding of the present disclosure, the presentdisclosure will be described in more detail below with reference toaccompanying drawings. Preferred embodiments of the present disclosureare provided in the accompanying drawings. However, the presentdisclosure may be embodied in different forms and is not limited to theembodiments described herein. Rather, these embodiments are provided sothat this disclosure will be clear and thorough.

Following concepts are used herein:

Writing board: boards for writing content in a variety of scenes, suchas teaching or meetings, and include, but are not limited to,blackboards, green-boards, and blue-boards, whiteboards. A writing boardto which the present disclosure relates include, but is not limited to,the blackboard, the green-board, the blue-board, and the whiteboard, andeven an electronic board, and for convenience and brevity of followingdescription, these writing media are collectively referred to herein aswriting boards. Wherein white or light color writing boards are calledas light board; dark color writing boards such as blackboard andgreen-board are called dark color writing board.

Board writing content: contents written on the writing board include,but are not limited to, the embodiment in form of words, symbols,diagrams, and the like, and the embodiment of the board writing contentis collectively referred to as characters in the present disclosure.

Gray scale image: an image represented in grayscale. Any non-grayscaleimage may be converted to the gray scale image. Specifically, since anycolor is composed of three primary colors of red, green and blue, if acolor of a certain pixel point is originally represented as (R, G, B) ina RGB space, a gray level Gray of the pixel point after being convertedinto the gray scale image is R, G, B weighted sum.

However, a video for teaching mentioned in the related art may cause thewriting contents of the board writing presented by the video notcomplete because of a teacher blocking the writing board. Therefore, ina scheme of completing the board writing content extraction and shieldedcontent, by extracting the board writing content form a video shot onsite, the shielded content is completed to obtain a complete boardwriting content, and finally the complete board writing content and thevideo shot on site are synthesized to obtain a video without shieldingof the board writing, so that students watching courses through thevideo cannot miss important contents because of the teacher shieldingthe board writing, and a classroom experience of the students is greatlyimproved. Of course, this process may also be applied to video inscenarios such as meetings, training, etc.

However, in the video shot on site, some slight differences exist amongboard writing images of consecutive frames, wherein the difference ofhandwriting edges of board writing contents may cause a phenomenon thathandwriting bounces exist in the board writing contents viewed by humaneyes when the video is played, and the handwriting bounces mean that thehandwriting edges of a same handwriting at a same position consecutivelybounce when the same handwriting at the same position is viewed, so thatan impression is influenced.

FIG. 1 is a flowchart of a video processing method according to anembodiment of the present disclosure. As shown in the reference figure,following steps are included.

In step S100, acquiring a board writing image of consecutive frames froma video with unobstructed board writing.

In step S110, taking the board writing image of a first frame in theconsecutive frames as a reference image.

Wherein, the video with unobstructed board writing in step S100 requiresthat board writing content in the board writing image of each frame inthe corresponding video is completely presented. Since a teacher mayteach through writing content on a writing board in a teaching scene, ifthe teacher shields the writing content at a certain moment when isteaching, a phenomenon that the writing content in the image of acertain frame is shielded appears in the video, so that an originalvideo obtained through shooting by a camera is not the video withunobstructed board writing, and the video with unobstructed boardwriting may be obtained through a scheme of extracting the writingcontent and completing a shielded content. An exemplary frame image inthe video with unobstructed board writing obtained by the scheme isshown in FIG. 2 , and it may be seen from the drawing that the boardwriting content may be completely presented, and the teacher as atransparent layer does not influence complete presentation of the boardwriting content.

Operations of steps S100 and S110 include: taking the video withunobstructed board writing as an input of this step, acquiring boardwriting images of consecutive frames from a moment when the video startsto have the board writing content, then taking the board writing imageof a first frame in the consecutive frames as a reference image of aprimary cycle, and then taking one of the board writing images from theconsecutive frames as the board writing image of a current frame. Here,the board writing image refers to an image having the board writingcontent.

In step S120, calculating a plurality of difference areas between theboard writing image of the current frame and the reference image, andobtaining at least one difference area having a difference greater thana difference threshold.

It is known that different video streams use different color spaces,such as RGB and YUV. An example of RGB is used to illustrate how thisstep should be calculated. In a RGB color space, R values, G values, andB values are used to represent each pixel point in the frame image, andeach frame image includes, for example, 640×480 pixel points, and then amaximum value of the R values, G values, and B values is 255, a minimumvalue is 0, when RGB is 255, a presented color is white, and when RGB is0, the presented color is black.

As an embodiment of this step, based on RGB, calculating average RGBvalues of each pixel of an extracted board writing image and thereference image respectively, and a formula is: average RGB value=(Rvalue+G value+B value)/3, then comparing the average RGB values of theextracted board writing image and the reference image in a correspondingposition, and if a difference value is greater than a preset differencethreshold value, recording the corresponding position of the pixel in afirst set, and finally constructing a difference area according to thefirst set. FIG. 3 a and FIG. 3 b are used for illustrating correspondingimage blocks X1 and X2 of two images in a reference area, but it shouldbe noted that the image blocks X1 and X2 shown on the figures are all ina regular form, but the difference area obtained by the presentembodiment may be in an irregular shape. Optionally, an irregular shapeddifference area is expanded to be in a regular shape to facilitatesubsequent steps. In addition, the present embodiment may output two ormore difference areas.

As another embodiment of this step, based on RGB, converting theextracted board writing image and the reference image into gray scaleimages, and then comparing corresponding pixels in two grayscale imagesbased on the above embodiment to obtain the difference area.

As a third embodiment of this step, based on RGB, since a differencebetween board writing images of two consecutive frames is very small,the extracted board writing image and the reference image may be dividedinto a plurality of image blocks, then calculating average values of allR values, G values, and B values of each image block, comparing theaverage values of the corresponding image blocks, then extracting anddividing the image block whose difference is greater than a firstthreshold into a plurality of image blocks, calculating an average valueof a sum of all R values, G values, and B values of each image block,comparing the average values of the corresponding image blocks,acquiring the image block whose difference is greater than a secondthreshold, and so on, until the image block whose difference is greaterthan an Nth threshold is obtained, and acquiring the difference areaaccording to the image block whose difference is greater than the Nththreshold. It is to be understood that the first through Nth thresholdsmay be different, for example, gradually increasing.

In step S130, replacing a corresponding image block in the board writingimage of the current frame with a corresponding image block in thereference image to obtain a new board writing image for each of thedifference area of the at least one difference area.

In step S140, taking out the board writing image of a next frame fromthe consecutive frames.

Steps S130 and S140 may continue to refer to FIG. 3 b , assuming that X2is an image block whose difference area corresponds to the referenceimage and X1 is an image block whose difference area corresponds to theextracted board writing image, then replacing X1 with X2 to obtain thenew board writing image, and replacing the reference image with the newboard writing image, and then taking out the board writing image of thenext frame from the video with unobstructed board writing.

In step S150, judging whether the board writing image of the next frameexists. A final operation of step S140 is to take out the board writingimage of the next frame from the consecutive frames, if this operationis successful, it indicates that the board writing image of the currentframe is not the board writing image of a last frame, and the boardwriting image of the next frame exists, it jumps to step S120, and ifthis operation is failed, it indicates that the board writing image ofthe current frame is the board writing image of a last frame, and theboard writing image of the next frame does not exist, it jumps out of aloop, and step S160 is executed.

In step S160, outputting a plurality of new board writing images to forma new video.

In the present embodiment, the reference image is the board writingimage associated with the board writing image of the current frame,which is changed in the loop, so that a new reference image may beobtained anew at the end of each loop. With reference to the drawings,that is, in the loop includes steps S120 to S150, the reference image ofthe first loop is the first frame board writing image in the consecutiveframes, but at the end of each loop, a new reference image may be newlyobtained, which is still the board writing image associated with theboard writing image of the current frame, and then the next loop isperformed based on the new reference image. An end condition of the loopis to take out all the board writing images. After the loop is executed,a plurality of board writing image are obtained, the new board writingimages are combined into the new video according to a time sequence, andframes in the new video are associated, so that the phenomenon ofhandwriting bounces is avoided.

To illustrate the above embodiments, a more specific example (exampleone) is set forth. For example, if the video with unobstructed boardwriting is Video_input={f1, f2, . . . , fn}, n is a positive integer,and f1 to fn represent temporally consecutive frame images, in a firstloop, comparing f1 and f2 to obtain the difference area, image blockscorresponding to the difference area in f1 and f2 are f1_patch andf2_patch respectively, and then replacing f1_patch in f1 with f2_patchto obtain f2′; then in a second cycle, comparing f2′ and f3′ to obtainthe difference area, image blocks corresponding to the difference areain f2′ and f3′ are f2′_patch and f3_patch respectively, and thenreplacing f2′_patch in f2′ with f3_patch to obtain f3′; and so on,finally (n−1) frame images f2′ to fn′ are obtained, and then a sequenceVideo_input={f1, f2′, . . . , fn′} is output as the new Video.

In other examples, a time interval may be lengthened, refreshing onceevery interval of n1 frames, that is, reselecting an initial referenceimage every interval of n1 frames. For example, the video withunobstructed board writing is Video_input={f1, f2, . . . , fn1, fn1+1 .. . , fn}, wherein fn1 is a frame in middle, and all sequences beforefn1 are processed to {f1, f2′, . . . , fn1′} according to the previousexample one. When fn1+1 is processed, a difference calculation is notperformed (no processing is performed), and fn1+1 is output directly(served as a role of f1 in the previous processing stage, and served asthe reference image), and following sequence is executed again accordingto the example one to obtain {fn1+1, . . . , fn′}. A resulting timesequence is {f1, f2′, . . . , fn1′, fn1+1, . . . , fn′}, wherein fn1+1is equivalent to a frame of refresh, thus achieving an effect of overalldebounce.

In some embodiments, the reference image of a first loop may be anotherimage, for example, fusing images of several frames without a boardwriting content of the video with unobstructed board writing, and afused image serves as the reference image, or shooting a board writingimage without the board writing content with appropriate light and angleas the reference image by using a camera device.

In some embodiments, for each frame image in above sequence, for example{f2′, . . . , fn′}, edge smoothing and enhancement processing ofcharacter, which makes line thickness of the character as uniform aspossible and renders black within stroke, may also be performed. Theedge smoothing and enhancement processing of the character enable linesof each character of the board writing content to be thicker andclearer, and therefore a phenomenon that the board writing is uncleardue to the image block replacing step is avoided.

Since the writing board and the writing board content in the video withthe writing board unobstructed are often replaced by a white writingboard and a black writing board content or replaced by a black writingboard and a white writing board content, which is not associated with anoriginal color of the writing board, and immersion and interestingnessare slightly poor when the writing board is in transparent display.Thus, as a preferred embodiment, a color of the writing board may alsobe controlled, where the color of the writing board may be used as abackground color for entire video. Control of the color of the writingboard may be set as a selectable item and controlled by correspondingcommand parameters. For example, if a color control of the writing boardis started, a base color of the writing board or the color of thewriting board preset by the user is used for displaying, the steps inFIG. 4 are executed to process to obtain an image with the base color ofthe writing board or the color of the writing board preset by the user,otherwise, a default color of the writing board and the color of theboard writing content are used for outputting the video, if the writingboard is a dark color writing board, a default background color isblack, and the handwriting is white, and if the writing board is a lightcolor writing board, the default background color is white and thehandwriting is black.

In step S410, obtaining a corrected board writing image I_(rgb), whereinthe corrected board writing image only comprises a writable effectivearea, and comprise no frame of the writing board and no board writingcontent. The corrected board writing image I_(rgb) may be obtainedaccording to an original video.

In step S420, calculating an average value of each color channel of thecorrected board writing image, wherein an average value of the R channelis R_mean which is obtained by accumulating R value of all pixels anddivide it by a total number of pixels, an average value of the G channelis G_mean which is obtained by accumulating G value of all pixels anddivide it by a total number of pixels, an average value of the B channelis B_mean which is obtained by accumulating B value of all pixels anddivide it by a total number of pixels.

In step S430, acquiring the board writing image with a background coloras a base color according to the average value of each color channel,for example, for each pixel point in the dark color writing board, ifthe R value of the pixel point is smaller than a first threshold, the Rvalue of the pixel point is replaced by the R_mean, otherwise, the Rvalue of the pixel point is retained, the steps of judging and replacingthe G value and the B value of each pixel point are performed by thesame scheme, and finally, the writing board in the board writing imageis replaced by the dark color writing board. However, for each pixelpoint in the light color writing board, if the R value of the pixelpoint is greater than a second threshold, the R value of the pixel pointis replaced by the R_mean, otherwise, the R value of the pixel point isretained, the steps of judging and replacing the G value and the B valueof each pixel point are performed by the same scheme, and finally, thewriting board in the board writing image is replaced by the light colorwriting board. The first threshold and the second threshold may be setby themselves, for example, to be intermediate values between 0 and 255.

In addition, if the writing board is desired to be set to a color of thewriting board preset by the user, for a dark color writing board, if theR value, G value or B value of a pixel is smaller than a correspondingthreshold, constant value of the corresponding color channel preset bythe user is used to fill and replace the R value, G value or B value ofthe pixel, and for a light color writing board, the constant value ofthe corresponding color channel preset by the user is used to fill andreplace the R value, G value or B value of the pixel.

The present disclosure also proposes a video processing device, as shownin FIG. 5 . The device 500 includes a board writing debouncing module510 and a board writing background color control module 520. The boardwriting debounce module 510 may perform the video processing methodmentioned in the above embodiments (excluding the embodiment of FIG. 4 )to obtain the new video, which does not have the problem of handwritingshake in the picture due to an association between the board writingimages of the consecutive frames.

The board writing background color control module 520 is used forcontrolling the background color of the writing board in an outputvideo. In particular, the color of the writing board may be controlledusing a command parameter, which may determine, for example, whether touse the default background color or an original base color of thewriting board. If the original base color of the writing board is used,the steps of FIG. 4 may be followed. The board writing background colorcontrol module 520 is capable of achieving a control of the backgroundcolor of the board writing in a transparent display process of the boardwriting image, so that the picture is closer to a real scene.

It should be understood that, when the board writing debouncing module510 and the board writing background color control module 520 areimplemented as computer programs, they may be independent of each other,and both of the two function modules may be implemented as plug-inlibraries for user and software and hardware platform to call.

In conclusion, through the module or the method, a generated video isstable in picture display and has a presentation effect close to thereal scene, so that understanding and memorizing of the board writingcontents by students may be guaranteed, and a classroom substitutionfeeling is enhanced.

An electronic device 1300 is further provided in an embodiment of thepresent disclosure, as shown in FIG. 6 , and includes a memory 1310, aprocessor 1320, and a program that is stored in the memory 1310 and isexecutable on the processor 1320, and when the program is executed bythe processor 1320, the program may implement each process of eachembodiment in the video processing method, and may achieve a sametechnical effect, and in order to avoid repetition, details are notrepeated here. Of course, the electronic device may also includeauxiliary sub-devices such as a power supply 1330, a network interface1340, and an input-output interface 1350.

It will be understood by those skilled in the art that all or part ofthe steps of the methods of the above embodiments may be performed byinstructions or by instructions controlling associated hardware, and theinstructions may be stored in a computer readable storage medium andloaded and executed by a processor. Therefore, the disclosed embodimentsalso provide the computer readable storage medium, on which a computerprogram or instructions are stored, which, when executed by a processor,may implement the processes of the embodiments in the video processingmethod described above. The computer readable storage medium may be aUSB disk, a removable hard disk, a Read-Only Memory (ROM), a RandomAccess Memory (RAM), a magnetic disk, or an optical disk, which iscapable of storing program codes.

Since the instructions stored in the readable storage medium can executethe steps in any video processing method provided in the embodiments ofthe present disclosure, beneficial effects that may be achieved by anyvideo processing method provided in the embodiments of the presentdisclosure may be achieved, which are detailed in the foregoingembodiments and will not be described again here. The above operationsmay be implemented in the foregoing embodiments, and are not describedin detail herein.

FIG. 7 is a schematic diagram of a teaching system according to anembodiment of the present disclosure. The teaching system includes: acamera device 701, a processing device 702, and a display device 703.The camera device 701 is used to take a video. The processing device 702is electrically connected to the camera device to receive a video fromthe camera device, and is capable of converting the video into a videowith board writing unobstructed according to the method provided in thisspecification or other methods, then executes the video processingmethod provided in each of the above embodiments, and outputs a newvideo. The display device 703 is used to display the new video output bythe processing device 702 on a display screen. It will be appreciatedthat the teaching system may be integrated into an electronic productincluding components such as a camera, a display, and a processor, onthe one hand, and may be implemented as a plurality of devicescommunicating through a network (e.g., a local area network), on theother hand.

It should be noted that, in the description of the embodiments, thedifferences from the other embodiments are emphasized, and the same orsimilar parts between the embodiments can be understood by referring toeach other. For system embodiments, reference is made to the descriptionof the method embodiment section for the sake of substantial similaritywith the method embodiments.

Further, it is noted that in the device and method of the presentdisclosure, it is apparent that each component or each step may bedecomposed and/or recombined. The decomposition and/or recombination areto be considered equivalents of the present disclosure. Also, the stepsof performing the series of processes described above may naturally beperformed chronologically in the order described, but need notnecessarily be performed chronologically, and some steps may beperformed in parallel or independently of each other. It will beunderstood by those of ordinary skill in the art that all or any of thesteps or components of the methods and device of the present disclosuremay be implemented in any computing device (including processors,storage media, etc.) or network of computing devices, in hardware,firmware, software, or any combination thereof, which can be implementedby those of ordinary skill in the art using their basic programmingskills after reading the description of the present disclosure.

Finally, it should be noted that: it should be understood that the aboveexamples are only for clearly illustrating the present disclosure, andare not intended to limit the embodiments. Other variations andmodifications will be apparent to persons skilled in the art in light ofthe above description. And are neither required nor exhaustive of allembodiments. And obvious changes and modifications can be made withoutdeparting from the scope of the present disclosure.

1. A video processing method, comprising: acquiring board writing imagesof consecutive frames from a video with unobstructed board writing;calculating a difference area between the board writing image of acurrent frame and a reference image; replacing a corresponding imageblock in the board writing image of the current frame with acorresponding image block in the reference image to obtain a new boardwriting image for each of the difference area; outputting the new boardwriting image to form a new video, wherein the board writing image ofthe current frame are sequentially each board writing image after theboard writing image of a first frame in the board writing images of theconsecutive frames, and the reference image is the board writing imageassociated with a previous board writing image.
 2. The video processingmethod according to claim 1, wherein for the board writing image of asecond frame in the board writing images of the consecutive framesserved as the board writing image of the current frame, the referenceimage is the board writing image of the first frame, and for the boardwriting image after the second frame served as the board writing imageof the current frame, the reference image is a new board writing imageassociated with a previous board writing image.
 3. The video processingmethod according to claim 1, wherein for the board writing image of asecond frame in the board writing image of the consecutive frames servedas the board writing image of the current frame, the reference image isan image obtained by fusing images of a plurality of frames without aboard writing content in the video with unobstructed board writing. 4.The video processing method according to claim 1, wherein the video withunobstructed board writing is obtained by following steps: extracting aboard writing content from an original video; completing the boardwriting content shielded by a teacher; and synthesizing a completedboard writing content with the original video.
 5. The video processingmethod according to claim 1, wherein calculating a difference areabetween the board writing image of a current frame and a reference imagecomprises: calculating a difference in pixel level between the boardwriting image of the current frame and the reference image, andobtaining the difference area based on pixels with the difference largerthan a difference threshold value, or, dividing the board writing imageof the current frame and the reference image into a plurality of imageblocks respectively, and taking the image block with a difference of theimage blocks larger than a difference threshold as the difference area.6. The video processing method according to claim 5, further comprising:expanding an irregular shaped difference area to a regular shapeddifference area.
 7. The video processing method according to claim 1,further comprising: adjusting a color of a writing board in the newboard writing image.
 8. The video processing method according to claim7, wherein adjusting a color of a board in the new board writing imagecomprises: obtaining a corrected board writing image, wherein thecorrected board writing image only comprises a writable effective area,and comprise no frame of the writing board and no board writing content;calculating an average value of each color channel of the correctedboard writing image or obtaining a constant value of each color channelpreset by a user; for a dark color writing board, modifying a pixelvalue of each color channel in the new board writing image, which issmaller than a first threshold value, into an average value of the colorchannel or a constant value of each color channel preset by a user; andfor a light color writing board, modifying a pixel value of each colorchannel in the new board writing image, which is larger than the secondthreshold value, into an average value of the color channel or aconstant value of each color channel preset by a user.
 9. A videoprocessing device, comprising: a board writing debouncing module forperforming the video processing method according to claim 1 andoutputting the new board writing image; and a board writing backgroundcolor control module for adjusting a color of a writing board in the newboard writing image.
 10. The video processing device according to claim9, wherein for the board writing image of a second frame in the boardwriting images of the consecutive frames served as the board writingimage of the current frame, the reference image is the board writingimage of the first frame, and for the board writing image after thesecond frame served as the board writing image of the current frame, thereference image is a new board writing image associated with a previousboard writing image.
 11. The video processing device according to claim9, wherein for the board writing image of a second frame in the boardwriting image of the consecutive frames served as the board writingimage of the current frame, the reference image is an image obtained byfusing images of a plurality of frames without a board writing contentin the video with unobstructed board writing.
 12. The video processingdevice according to claim 9, wherein the video with unobstructed boardwriting is obtained by following steps: extracting a board writingcontent from an original video; completing the board writing contentshielded by a teacher; and synthesizing a completed board writingcontent with the original video.
 13. The video processing deviceaccording to claim 9, wherein calculating a difference area between theboard writing image of a current frame and a reference image comprises:calculating a difference in pixel level between the board writing imageof the current frame and the reference image, and obtaining thedifference area based on pixels with the difference larger than adifference threshold value, or, dividing the board writing image of thecurrent frame and the reference image into a plurality of image blocksrespectively, and taking the image block with a difference of the imageblocks larger than a difference threshold as the difference area. 14.The video processing device according to claim 13, wherein the boardwriting debouncing module is further configured for performing the videoprocessing by: expanding an irregular shaped difference area to aregular shaped difference area.
 15. An electronic device, comprising: aprocessor, a memory and a program stored in the memory and executable onthe processor, wherein the program carries out steps of the videoprocessing method according to claim 1 when executed by the processor.16. A computer readable storage medium, a computer program or aninstruction is stored in the computer readable storage medium whichcarries out steps of the video processing method according to claim 1when executed by the processor.